Slightly squeamish father-to-be Tom Partleton had considered waiting outside the hospital room while his first child was born.

But when his wife, Emma, realised her labour was further advanced than she thought, Tom rose to the challenge.

Emma delivered their son, George James Partleton, in the family's bathtub in the early hours of August 19, assisted by her squeamish husband.

A surprise water birth is amazing enough, but Emma said she was most impressed with Tom keeping himself together.

"The most amazing thing about this is that Tom faints at everything," Emma said.

"The sight of blood, needles, I have even been to the optometrist with him before and they flipped his eyelids and he fainted.

"How he managed to stay in control just astounds me.''

The Partletons had been planning a water birth at Sunshine Coast Private Hospital, and George was due in another week.

They had finished a hypnobirthing course only days before they had to put what they learnt into practice.

"I was 38 weeks pregnant and was looking forward to meeting my little man soon as I was thinking he was still a week away," Emma said.

Her little man had other ideas. Her labour started at their home in Ilkley, Queensland, at 12.30am, and her bags weren't even packed yet. Even the hospital advised her to go back to bed and get more sleep, expecting the birth to be hours away.

Emma got into the bath to help ease the pain at around 2.15am and it definitely worked. The next thing she felt like "my body was pushing".

Before she knew it, the baby's head was coming out.

Tom gently guided the baby out and placed the umbilical cord on his wife's chest while waiting for an ambulance.

"We had about five minutes of precious time where it was just the three of us before the ambulance arrived. It was magical and I couldn't believe it," Emma said.